Changing the beat a notes on

If I understand your request,
https://musescore.org/en/handbook-advanced-topics/note-input-modes#rhyt…
'3, Entering rests is similar to adding dotted notes. Press the 0 key to toggle entering rests.'

See also:
https://musescore.org/en/node/21495

Are you referring to the first measure being a pickup where piece starts with two quavers just before the barline? If so, then right-click on the measure and change its Actual Time to 1/4 then enter your notes. If itś an ordinary 4/4 measure in the middle of a piece then enter three quarter-beat rests and the your notes.

Indeed, as others have said, normally you enter the rests first, then the notes - left to right, just like you read. Or, if you are talking about a pickup measure, shorten the measure first, then enter the notes.

However, if you are in a situation where for whatever reason you have already entered notes into one place and now decide you want them somewhere else instead, use cut & paste to move them. Select the two notes (eg, click the first, Shift+right to extend select to the second), Ctrl+X to cut, click the desired destination, Ctrl+V to paste. But there probably isn't anything there on beat 4 right now unless you enter some rests, so you'll need to do that anyhow, most likely.